Collected Evidence: Collected Evidence: Create mounds or hollows before planting trees/shrubs: freshwater wetlands Three studies evaluated the effects, on vegetation, of creating mounds or hollows in freshwater wetlands before planting trees/shrubs. All three studies were in the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study of 10-year-old restored/created freshwater wetlands in the USA reported that adding coarse woody debris to wetlands before planting trees/shrubs affected the composition of the ground vegetation layer, but not the tree layer. Overall richness/diversity (2 studies): Two studies in freshwater wetlands in the USA reported that creating mounds or hollows before planting trees/shrubs had no clear or significant effect on plant species richness and diversity 10–12 years later. In one of the studies, the same was true for bryophyte, herb and woody plants richness separately. VEGETATION ABUNDANCE   VEGETATION STRUCTURE Height (1 study): One replicated, paired, controlled study in created freshwater wetlands in the USA found that the average height of white cedar Thuja occidentalis saplings typically increased more, between two and five years after planting, in created mounds than on lower (occasionally flooded) ground. OTHER                                         Survival (1 study): One replicated, paired, controlled study in created freshwater wetlands in the USA found that white cedar Thuja occidentalis seedlings had higher survival rates when planted into created mounds than on lower (occasionally flooded) ground. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3288https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3288Sat, 10 Apr 2021 17:35:08 +0100Collected Evidence: Collected Evidence: Add upland topsoil before/after planting non-woody plants: freshwater wetlands Three studies evaluated the effects, on vegetation, of adding upland topsoil to freshwater wetlands planted with emergent, non-woody plants. Two studies were in the USA and one was in Canada. One study was in a greenhouse. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, randomized, paired, controlled study in freshwater trenches in Canada found that adding a mixture of mineral soil and peat to pots of mine tailings before planting water sedge Carex aquatilis typically increased its above-ground biomass two growing seasons later. VEGETATION STRUCTURE Individual plant size (2 studies): One replicated, controlled study in a greenhouse in the USA found that mixing topsoil into pots of mineral soil/compost before planting tussock sedge Carex stricta seedlings typically increased the biomass and number of shoots they developed over three months. However, one replicated, paired, controlled study in a wet meadow restoration site in the USA reported that mixing topsoil into the mineral soil/compost substrate before planting tussock sedge seedlings had no clear effect on the number of shoots they developed over two months. OTHER Survival (1 study): One replicated, randomized, paired, controlled study in freshwater trenches in Canada found that adding a mixture of mineral soil and peat to pots of mine tailings either increased or had no significant effect on survival of planted water sedge Carex aquatilis over two growing seasons. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3296https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3296Sun, 11 Apr 2021 08:11:14 +0100Collected Evidence: Collected Evidence: Add lime or similar chemicals before/after planting non-woody plants: brackish/saline wetlands Three studies evaluated the effects, on vegetation, of adding neutralizing chemicals to brackish/saline wetlands planted with emergent, non-woody plants. Two studies were in Canada. One study was in the USA. One study was in a greenhouse. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Characteristic plant abundance (1 study): One replicated, paired, controlled, before-and-after study in salt-contaminated bogs in Canada reported that liming reduced the above-ground biomass of planted salt marsh vegetation after one year. Individual species abundance (2 studies): One controlled study in former borrow pits in the USA found that limed and unlimed plots supported similar biomass of a planted herb species after 1–2 growing seasons. In contrast, one replicated, randomized, paired, controlled study in salt-contaminated peat in Canada found that limed pots supported lower biomass of two sown herb species than unlimed pots, after four months. VEGETATION STRUCTURE   OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in salt-contaminated peat in Canada found that for each of two sown herb species, germination rates were similar in limed and unlimed pots. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3301https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3301Sun, 11 Apr 2021 08:46:32 +0100Collected Evidence: Collected Evidence: Add inorganic fertilizer before/after planting non-woody plants: freshwater wetlands Four studies evaluated the effects, on vegetation, of adding inorganic fertilizer to freshwater wetlands planted with emergent, non-woody plants. Two studies were in the USA, one was in the Netherlands and one was in Ireland. One of the studies in the USA was in a greenhouse. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, paired, controlled study of lakeshores planted with bulrushes Scirpus spp. in the Netherlands found that fertilized and unfertilized plots contained a similar amount (density and biomass) of each bulrush species over three growing seasons. VEGETATION STRUCTURE Individual plant size (2 studies): Two replicated, controlled studies (one also paired) in the USA found that adding fertilizer to mineral soil increased the biomass and/or number of shoots of tussock sedge Carex stricta seedlings, 2–3 months after planting. However, in both studies, adding fertilizer had no significant or clear effect on sedge size in plots amended with compost and/or topsoil. OTHER Growth (1 study): One replicated, paired, controlled, before-and-after study in tubs of mining waste in Ireland found that adding fertilizer increased growth of planted sweetgrass Glyceria fluitans in one case but had no significant effect in another. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3304https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3304Sun, 11 Apr 2021 08:57:08 +0100Collected Evidence: Collected Evidence: Add inorganic fertilizer before/after planting non-woody plants: brackish/saline wetlands Seven studies evaluated the effects, on vegetation, of adding inorganic fertilizer to brackish/saline wetlands planted with emergent, non-woody plants. Four studies were in the USA. Two of these were based in the same marsh, but used different experimental set-ups. Two studies were in Canada. One study was in China. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Overall abundance (2 studies): One replicated, randomized, paired, controlled study in intertidal brackish marshes in Canada found that adding fertilizer when planting wetland herbs typically had no significant effect on total live vegetation biomass, after two growing seasons. One replicated, paired, controlled, before-and-after study in salt-contaminated bogs in Canada found that overall vegetation biomass and cover were greater in fertilized than unfertilized plots, one year after introducing salt marsh vegetation. Individual species abundance (6 studies): Six studies quantified the effect of this action on the abundance of individual plant species. For example, three replicated, randomized, paired, controlled studies in intertidal areas in the USA found that the abundance of cordgrasses Spartina spp. was typically similar in fertilized and unfertilized plots, 1–2 growing seasons after planting. This was true for density, biomass and/or cover. However, one controlled study on former borrow pits in the USA found that cordgrass Spartina spp. biomass was typically greater in fertilized than unfertilized plots, one growing season after planting. This study also found that fertilization typically reduced black rush Juncus roemarianus biomass, one growing season after planting. VEGETATION STRUCTURE Height (6 studies): Five replicated, controlled studies (four also paired, three also randomized) in brackish/saline wetlands in the USA, China and Canada found that adding fertilizer had no significant effect on the height of planted/sown wetland herbs after 1–2 growing seasons. One controlled study on former borrow pits in the USA found that fertilized smooth cordgrass Spartina alterniflora was taller than unfertilized smooth cordgrass, two growing seasons after planting. OTHER Survival (4 studies): Three replicated, randomized, paired, controlled studies in intertidal areas in the USA and Canada found that adding fertilizer had no significant effect on the survival of planted wetland herbs over 1–2 growing seasons. One controlled study on former borrow pits in the USA reported that adding standard fertilizer to planting holes reduced the survival of planted big cordgrass Spartina cynosuroides, after one growing season. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3305https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3305Sun, 11 Apr 2021 08:57:23 +0100Collected Evidence: Collected Evidence: Add below-ground organic matter before/after planting non-woody plants: freshwater wetlands Seven studies evaluated the effects, on vegetation, of adding below-ground organic matter to freshwater wetlands planted with emergent, non-woody plants. All seven studies were in the USA. Two of the studies were in a greenhouse. VEGETATION COMMUNITY Overall richness/diversity (1 study): One replicated study of marshes alongside a stream in the USA found that adding compost before planting wetland herbs typically reduced overall plant species richness over the following three growing seasons. Richness was negatively related to the amount of soil organic matter in plots. VEGETATION ABUNDANCE Overall abundance (1 study): One replicated study of marshes alongside a stream in the USA found that adding compost before planting wetland herbs had no significant effect on total vegetation biomass after three growing seasons. Biomass was not significantly related to the amount of soil organic matter in plots. Characteristic plant abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in an experimental wet basin in the USA found that adding sawdust to plots before sowing a mixture of target sedge meadow species had no significant effect on the density of target species overall or target grass-like species. Adding sawdust sometimes affected the density of target forbs, depending on the presence/diversity of a nurse crop. Individual species abundance (2 studies): Two replicated, randomized, paired, controlled studies in wetlands in the USA quantified the effect of this action on the abundance of individual plant species. One study found that incorporating woodchips into soil mounds before planting tussock sedge Carex stricta reduced total tussock sedge cover after two growing seasons. The other study reported varying effects of sawdust addition on the abundance of individual plant species, depending on factors such as the species and presence/diversity of a nurse crop. VEGETATION STRUCTURE Individual plant size (4 studies): Three replicated, controlled studies (one also paired) in the USA found that mixing compost into the substrate before planting tussock sedge Carex stricta seedlings typically increased the biomass and/or number of shoots they developed over 2–3 months. However, in one of the studies, compost typically had no significant effect on top of other soil amendments. One replicated, randomized, paired, controlled study in a wetland in the USA found that incorporating woodchips into soil mounds had no significant effect on the biomass of planted tussock sedge Carex stricta, over two growing seasons. OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in an experimental wet basin in the USA found that seeds of mixed sedge meadow species had a similar germination rate, over 16 weeks after sowing, in plots with or without added sawdust. Survival (2 studies): One replicated, randomized, controlled study in an excavated wetland in the USA found that planted lurid sedge Carex lurida tubers had a higher survival rate, after one year, in plots that had been amended with leaf litter than in unamended plots. One replicated, randomized, paired, controlled study in a wetland in the USA found that incorporating woodchips into soil mounds increased survival of planted tussock sedge Carex stricta in a drier area, but reduced its survival in a wetter area. Growth (1 study): One replicated, randomized, paired, controlled study in a wetland in the USA found that incorporating woodchips into soil mounds had no significant effect on the growth rate of planted tussock sedge Carex stricta, over two growing seasons. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3308https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3308Sun, 11 Apr 2021 09:50:48 +0100Collected Evidence: Collected Evidence: Add below-ground organic matter before/after planting non-woody plants: brackish/saline wetlands Six studies evaluated the effects, on vegetation, of adding below-ground organic matter to brackish/saline wetlands planted with emergent, non-woody plants. Five studies were in the USA and one was in China. Two studies were in the same marsh, but used different experimental set-ups. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Individual species abundance (5 studies): Three replicated, randomized, controlled studies in the USA found that adding organic matter before/after planting cordgrasses Spartina spp. typically had no significant effect on cordgrass abundance (biomass and/or density) after 1–2 growing seasons. One replicated, paired, controlled study in an estuary in the USA found that mixing kelp compost into the sediment before planting California cordgrass Spartina foliosa increased its density, three growing seasons later. One replicated, controlled, before-and-after study in an estuary in China found that mixing reed debris into the sediment before sowing seablite Suaeda salsa increased its biomass, but not its density, five months later. VEGETATION STRUCTURE Individual plant size (1 study): One replicated, randomized, paired, controlled study in an estuary in the USA found that tilling compost into plots before planting salt marsh vegetation typically increased the overall size of plants surviving after 1–2 growing seasons. Size was reported as a combination of height and lateral spread. Height (5 studies): Four replicated, controlled studies in the USA and China found that adding organic matter before/after introducing salt marsh plants (cordgrasses Spartina spp. or seablite Suaeda salsa) had no significant effect on their height after 1–2 growing seasons. One replicated, paired, controlled study in an estuary in the USA found that mixing kelp compost into the sediment before planting California cordgrass Spartina foliosa increased its height, three growing seasons later. OTHER Survival (1 study): One replicated, randomized, paired, controlled study in an estuary in the USA found that plots amended with kelp compost supported a higher survival rate of planted salt marsh vegetation over 1–2 growing seasons, with a similar but typically insignificant trend for survival rates of individual species. Growth (1 study): One replicated, randomized, controlled study in a greenhouse in the USA found that adding alginate after planting cordgrasses had no significant effect on the average number of shoots per plant, nine weeks later. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3309https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3309Sun, 11 Apr 2021 09:50:58 +0100Collected Evidence: Collected Evidence: Use fences or barriers to protect freshwater wetlands planted with non-woody plants Four studies evaluated the effects, on vegetation, of using fences or barriers to protect freshwater wetlands planted with emergent, non-woody plants. There was one study in each of Canada, the Netherlands, Israel and the USA. VEGETATION COMMUNITY Community composition (1 study): One replicated, site comparison study in the USA found that amongst planted/sown lakeshores, those protected with fences or wave breaks contained different wetland plant communities, after 1–6 years, than those without fences or wave breaks. VEGETATION ABUNDANCE Individual species abundance (1 study): One replicated, controlled study at the edge of a freshwater lake in the Netherlands found that amongst plots planted with lakeshore bulrush Scirpus lacustris, those from which wildfowl had been excluded contained a greater density and biomass of lakeshore bulrush, after 1–2 years, than those that remained open to wildfowl. VEGETATION STRUCTURE   OTHER Survival (2 studies): Two replicated, paired, controlled studies in freshwater wetlands in Canada and Israel reported that protecting emergent herbs, with silt screens or herbivore fencing, increased survival rates over 12–18 months after planting. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3328https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3328Sun, 11 Apr 2021 13:14:37 +0100Collected Evidence: Collected Evidence: Use fences or barriers to protect freshwater wetlands planted with trees/shrubs Five studies evaluated the effects, on vegetation, of using fences or barriers to protect freshwater wetlands planted with trees/shrubs. Four studies were in the USA and one was in Australia. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Tree/shrub abundance (1 study): One replicated, paired, controlled study in a floodplain swamp clearing in the USA found that amongst plots sown with tree seeds, fencing to exclude deer had no significant effect on total tree seedling density after three years. VEGETATION STRUCTURE Height (2 studies): One replicated, paired, controlled study in a floodplain swamp clearing in the USA found that amongst plots sown with tree seeds, those also fenced to exclude deer contained taller tree seedlings, after three years, than those left unfenced. One replicated, paired, controlled study in created freshwater wetlands in the USA found that the average height of white cedar Thuja occidentalis saplings typically increased by a similar amount, between two and five years after planting, in plots fenced to exclude deer and plots left unfenced. OTHER Survival (3 studies): One replicated, paired, controlled study in floodplain swamps in Australia reported that planted swamp gum Eucalyptus camphora seedlings had a much higher survival rate, over one year, in plots fenced to exclude mammals than in open plots. Two replicated, paired, controlled studies in freshwater wetlands in the USA reported that exclusion fencing sometimes increased survival of planted tree seedlings but sometimes had no clear or significant effect. This depended on factors such as the season of planting, seedling elevation, and site. Growth (1 study): One replicated, randomized, controlled study in a nutria-invaded wetland in the USA found that planted baldcypress Taxodium distichum seedlings grew more, over one growing season, when protected than when left unprotected. Plastic guards increased height and diameter growth rates. Sticky, insect-repellent oil increased the growth rate for height, but not diameter. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3330https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3330Sun, 11 Apr 2021 13:15:05 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted non-woody plants: freshwater wetlands Three studies evaluated the effects, on emergent non-woody vegetation planted in freshwater wetlands, of removing competing plants. All three studies were in the USA. Two studies used the same experimental wet basins but planted different species. VEGETATION COMMUNITY   VEGETATION ABUNDANCE Herb abundance (1 study): One replicated, randomized, paired, controlled study in wet meadows in the USA found removing an invasive species with herbicide before sowing mixed grass and forb seeds increased the total biomass of sown species after 1–2 growing seasons, but that burning to remove the invasive species had no significant effect on sown species biomass. Individual species abundance (1 study): One replicated, paired, controlled study in wet basins in the USA found that the effect of weeding to remove competitors on lake sedge Carex lacustris biomass and density, in the three years after planting, depended on the year and water level. VEGETATION STRUCTURE Height (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the height of planted sedges. One of the studies found that weeding had no significant effect on the height of planted tussock sedge Carex stricta in three of three years. The other study found that weeding reduced the average height of lake sedge Carex lacustris in the first year after planting, but had no significant effect in the following two years. OTHER Survival (2 studies): Two replicated, paired, controlled studies in wet basins in the USA examined the effect of weeding to remove competitors on the survival of planted sedges Carex spp. Both studies found that weeding had no significant effect on sedge survival in at least two of three years. One of the studies found that weeding affected tussock sedge Carex stricta survival in the second year after planting, but that the direction of the effect depended on plot elevation. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3332https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3332Sun, 11 Apr 2021 14:05:56 +0100Collected Evidence: Collected Evidence: Remove vegetation that could compete with planted trees/shrubs: freshwater wetlands Five studies evaluated the effects, on trees/shrubs planted in freshwater wetlands, of removing competing plants. Four studies were in the USA. Two of these took place in the same swamp, but with different experimental set-ups. One study was in Australia. VEGETATION COMMUNITY   VEGETATION ABUNDANCE   VEGETATION STRUCTURE Height (3 studies): Three replicated, controlled studies (two also randomized, two also paired) in a wet meadow in Australia and a degraded swamp in the USA found that clearing vegetation before planting tree/shrub seedlings typically had no clear or significant effect on their height, after 1–4 growing seasons. However, one of the studies in the USA found that planted baldcypress Taxodium distichum seedlings were taller, after three growing seasons, when planted amongst cut woody vegetation than below an uncleared canopy. Diameter/perimeter/area (1 study): One replicated, randomized, paired, controlled study in a wet meadow in Australia found that clearing vegetation, before planting tree/shrub seedlings, typically had no significant effect on the diameter of these seedlings nine months later. OTHER Germination/emergence (1 study): One replicated, randomized, paired, controlled study in a wet meadow in Australia found that there were more seedlings in plots that had been cleared of vegetation before sowing tree/shrub seeds, than in plots that had not been cleared before sowing. Seedlings were counted two months after sowing. Survival (4 studies): Three replicated, controlled studies (two also randomized, two also paired) in a wet meadow in Australia and a degraded swamp in the USA found that clearing vegetation before planting tree/shrub seedlings typically had no clear or significant effect on their survival, after 1–4 growing seasons. However, one of the studies in the USA found that planted baldcypress Taxodium distichum seedlings had a lower survival rate, after three growing seasons, when planted amongst cut woody vegetation than below an uncleared canopy. One replicated, randomized, paired, controlled study in degraded swamps in the USA found that removing reed canarygrass Phalaris arundinacea before planting tree/shrub seedlings never significantly reduced their survival rate over 1–2 growing seasons, and often increased it. Growth (1 study): One replicated, randomized, controlled study in the USA found that baldcypress Taxodium distichum seedlings planted into a marsh grew more in diameter, but less in height, when planted into plots cleared of vines than when planted into uncleared plots. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3334https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3334Sun, 11 Apr 2021 14:09:05 +0100
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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